The description sets out the currents in three separate circuits. In circuit P, the current remains constant at $0.52\ \text{A}$ in a single direction. In circuit Q, the current varies continuously from $0.25\ \text{A}$ to $0.35\ \text{A}$, but it always flows the same way. In circuit R, the current reaches a maximum value of $0.52\ \text{A}$ and reverses direction at regular intervals. Which of the circuits have a direct current?
- AP only
- BP and Q
- CQ and R
- DR only